This invention relates to a disk driver having a disk holding table for holding and rotating a disk such as a magnetic disk and, more particularly, to a disk driver having a pivotal support structure capable of defining a unique position of a support member arranged on a lower surface of a disk holding table.
In a disk driver of the type described, a disk holding table is provided with a circular engaging hole and a circular driving hole formed at different positions eccentric with a center of the disk holding table. To a lower surface of the disk holding table, a support member is attached by the use of the engaging hole and the driving hole.
The support member has one end provided with an insertion hole for insertion of a support pin. The support pin has an engaging end inserted through the insertion hole of the support member to be received in the engaging hole of the disk holding table. Thus, the support member is pivotally supported through the support pin to be rotatable with respect to the disk holding table. The other end of the support member opposite to the one end is a free end to which a driving roller is rotatably attached. The driving roller is upwardly protruded through the driving hole of the disk holding table.
It is noted here that the engaging end of the support pin allows the support member to be rotated in a radial direction of the disk holding table and to be displaced in an axial direction (vertical direction) of the support pin itself. Thus, a pivotal support structure is formed. In such a pivotal support structure, the insertion hole formed at the one end of the support member has a diameter greater than that of the engaging end of the support pin. This results in presence of a gap between a peripheral side wall of the engaging end of the support pin and a circumferential wall defining the insertion hole.
When such a gap is present, the support pin is displaced within the insertion hole following the movement of the support member so that the peripheral side wall of the engaging end of the support pin is brought into contact with the circumferential wall of the insertion hole along a single vertical line, namely, at a single point in a sectional plane. This is because each of the support pin and the insertion hole has a generally circular section. Throughout the specification, such contact is referred to as a single-line contact and sometimes as a single-point contact. In case of the single-point contact, a point of contact is shifted from place to place in accordance with variation of a force applied to the support member. Therefore, it is impossible to define a unique position of the support member. As a result, unfavorable wobbling of the disk holding table can not be sufficiently suppressed.